For those keeping score at home: The total number of U.S. prescriptions for generic drugs grew by 12% a year between 2004 and 2008, while the number of prescriptions for branded drugs fell by 6% a year during the same period, according to a new analysis from Wolters Kluwer Health. . . .

A bunch of familiar factors are driving this. Payers are being more pushy about getting patients to take generics. As big campaigns like Wal-Mart’s $4 generics deal have made generics more familiar, patients have grown more comfortable with the idea of moving off of branded drugs. Tough economic times and, for many patients, higher co-pays add an economic incentive. And some big name drugs have gone off patent, without being replaced by comparable new blockbusters (Merck’s Zocor — generic simvastatin — comes to mind). . . .